The invention relates to a wireless network with at least one base station and a plurality of associated terminals for exchanging user data and control data.
The document “ETSI SMG2, Meeting No. 24, Cork Ireland, 1-5 December 1997, Tdoc SMG2 359/97, Concept Group Alpha-Wideband Direct-Sequence CDMA (WCDMA), EVALUATION DOCUMENT (3.0), Part 1: System Description, Performance Evaluation” proposes a radio network operating on the basis of the CDMA (CDMA=Code-Division Multiple Access) method. The radio network comprises a plurality of radio cells with a their respective base station and terminals or mobile stations located in these radio cells. After the registration and synchronization of a terminal, for example, in the case of a request for a user channel, a terminal transmits a random access burst via a random access channel (RACH). The random access burst comprises a preamble part and a data part. The preamble part comprises 16 symbols (preamble sequence) which is spread by an orthogonal Gold code (preamble code). The Gold code contains 256 chip intervals. The data part contains a field with an identification for the terminal, a field for featuring the requested service (short packet transmission, dedicated-channel set-up etc.), an optional field for data packets (optional user packet) and a CRC field for error detection. A random access burst received by a base station is applied, via a matched filter, a preamble correlator and a peak detector, to a circuit section which estimates the time delay of the data part and controls a RAKE circuit for evaluating the data part. Thus, in this case use is made of peak detection based on a correlation, and subsequent message decoding. 80 random access channels are available to the terminals assigned to a base station. These channels are determined by 16 different preamble codes and 5 different transmission instants. If two or more terminals transmit via the same random access channel, i.e. the same preamble code and the same transmission instant are chosen, a collision is bound to occur and the information transmitted by the terminals cannot be evaluated correctly by the base station. Such collisions are likely notably in the case of high traffic loads.